Figure 8. Prazosin-sensitive and insensitive components of the endogenously evoked astrocyte process Ca²⁺ fluctuations recorded during in vivo startle responses.

a. Representative images of Ca²⁺ fluctuations from cortical astrocytes before, during and after startle responses. The upper panels show control responses to startle without prazosin influence, whereas the lower panels show the same field of view after 1 mg/kg prazosin was injected ip. Startle was evoked at 225 s. Representative data for WT are shown in Supplementary movie 8 and 9. b. Average traces showing Ca²⁺ responses in cortical astrocytes for somatic Ca²⁺ fluctuations before and after prazosin injections. Note that startle triggered a robust Ca²⁺ response in the somata, that was blocked by prazosin. c. Similar experiments to those shown in b, but for astrocytes from IP3R2^−/− mice. Note that startle evoked no somatic responses. d. As in b, but for astrocyte process Ca²⁺ fluctuations. Note that the responses in the processes displayed a fast component with a peak at ~3 s after startle, and a late component that persisted during these recordings. Prazosin blocked only the fast component. e. As in d, but for IP3R2^−/− mice. The slow component of the Ca²⁺ response triggered by startle was present in the IP3R2^−/− mice and was insensitive to prazosin. The results shown in this figure are from 4 WT and 4 IP3R2^−/− mice. In the interests of clarity, error bars in panels b–e are shown for every 5^th data point, but the underlying average traces are for all cells. The data are shown as mean ± s.e.m.